John Mondragon

Led the modernization of a critical sales front-end and back-end application that enabled users to order broadband, electricity, gas, and mobile services. The project was initiated to address two significant challenges: a legacy Knockout.js front end that was difficult to maintain and a monolithic C# .NET back end built on an outdated N-layer architecture.

Front-end refactor: Developed a new, performant front-end using React JavaScript to replace the legacy system. The new architecture provided a more modular and intuitive structure, which simplified the codebase, accelerated feature development, and dramatically reduced time spent on bug fixes.

Back-end modernization: Spearheaded a strategic refactoring effort on the C# .NET back end. Successfully migrated 40% of the core codebase from a tightly coupled N-layer architecture to a more scalable and maintainable Onion Architecture.

Quality and testing: As part of this refactoring, I introduced a robust testing framework and wrote over 650 new unit tests, resulting in a significant improvement in code quality and a substantial reduction in technical debt.

Maintained and enhanced a C#.NET web application that enabled users to sign up for broadband services from Tesco in the United Kingdom. My contributions focused on full-stack development, from front-end user experience to back-end logic and database management.

Technology stack: Developed using ASP.NET Core MVC and C# .NET, with a SQL Server back end. The front nd utilized JavaScript, jQuery, and Bootstrap to create a responsive and user-friendly interface.

Key features developed:

Address validation: Integrated with the Royal Mail Postcode Address File (PAF) API to implement a real-time address lookup and validation system, reducing data entry errors.

Service availability checker: Built a feature that integrated with a third-party API to instantly determine if a user's address was serviceable for TESCO's broadband offering.

Payment integration: Implemented a secure payment gateway integration to process customer payments during the sign-up process.

Provided subject-matter expertise and technical leadership in modern software architecture, specifically promoting the adoption of Onion Architecture and SOLID principles across the team.

Mentorship and knowledge sharing: Developed and led informal technical sessions and workshops, framing them as knowledge-sharing sessions to introduce team members to Onion Architecture. This was a direct response to issues with "spaghetti code" and tightly coupled components in our existing codebase.

Practical implementation: Demonstrated how to refactor existing modules to conform to Onion Architecture, resulting in cleaner, more maintainable, and highly testable code. This led to a significant increase in unit test coverage and reduced dependency on external frameworks.

Guiding design decisions: Actively guided the team in applying SOLID principles (single responsibility, open/closed, Liskov substitution, interface segregation, and dependency inversion) to component design, fostering a culture of writing modular and decoupled code.

Result: The team began to adopt these principles on new projects, leading to a demonstrable improvement in code quality and a reduction in post-deployment bugs.